The present invention relates to a distal stem centralizer for femoral prosthesis. In the prior art, centralizer mechanisms are known. However, Applicant is unaware of any such device including all of the features and aspects of the present invention.
ORTHOMET manufactures a femoral prosthesis including a centralizer mechanism having a stem which fits within a hole formed in the distal stem tip. The centralizer extends distally of the stem including blade-like appendages extending radially outwardly and into engagement with the intramedullary canal. This design has proven unreliable, in practice, in that, occasionally, the finned portion of the centralizer may break away from the stem portion which is received within the hole formed within the distal stem. Furthermore, the shape of the fins of this centralizer creates turbulence in the cement which is inserted within the intramedullary canal and through which the centralizer and distal stem of the femoral prosthesis travel as they are inserted within the intramedullary canal and through the cement to their location of final installation. Additionally, proximal movements of the distal stem during installation can dislodge this centralizer from the distal stem tip.
RICHARDS has developed a centralizer which will be described in greater detail with reference to FIGS. 1-3 herein. In using the RICHARDS centralizer, two mutually perpendicular slots are cut through the end of the distal stem and the RICHARDS centralizer which includes two crossed diametrical fins is inserted within the slots cut through the stem. The slots create four sharp corners as well as four thin stem tip portions which may weaken the distal stem and are difficult to create. Furthermore, this centralizer does not include any locking mechanism which would preclude accidental removal during installation. For example, if the surgeon is inserting a femoral prosthesis within the intramedullary canal of the proximal femur and, during insertion, must slightly pull the femoral prosthesis in the proximal direction, it is possible that this centralizer could be inadvertently removed and lost within the cement within the intramedullary canal, thus requiring complete removal of the cement as well as the centralizer and re-insertion of cement and installation of a new centralizer, thereby extending surgery time.
As such, a need has developed for a femoral prosthesis distal stem centralizer which is easy to install, requires only slight modification of the distal stem and which reliably locks in installed position. It is with these aspects in mind that the present invention was developed.